Modified polyethersulfone composite membrane material and preparation method thereof

Abstract

The invention discloses a modified polyethersulfone composite membrane material and a preparation method thereof, and relates to the technical field of composite membrane preparation, the preparation method comprises the following steps: dissolving polyethersulfone in a solvent, and adding a bromination reagent in batches for reaction; adding picolinic acid into the brominated polyethersulfone solution, heating and reacting under the protection of inert gas; cooling the system, slowly dropwise adding a europium salt solution into a solution containing picolinic acid modified polyethersulfone, and reacting under mild conditions; cooling and filtering the reaction liquid, pouring on a clean glass plate, scraping into a uniform liquid film, and volatilizing and drying at room temperature for a long time to remove the solvent; soaking and stripping the dried film, absorbing the surface moisture, and balancing in a dryer to obtain the modified polyethersulfone composite film material. According to the invention, a picolinic acid-europium ion coordination structure is constructed in situ in a polyether sulfone molecular chain, so that chemical bonding fixation of a luminescence center is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of composite membrane preparation, and in particular relates to a modified polyethersulfone composite membrane material and a preparation method thereof. Background Art

[0002] Polyethersulfone (PES) is an amorphous polymer and a thermoplastic engineering plastic, produced by the condensation of 4,4'-diphenyl ether bissulfonyl chloride with diphenyl ether in the presence of anhydrous ferric chloride. Due to its excellent properties, including heat resistance, hot water resistance, creep resistance, dimensional stability, impact resistance, chemical resistance, non-toxicity, and flame retardancy, it has long been widely used in electronics, electrical appliances, machinery, automobiles, medical devices, food processing, and non-stick coatings.

[0003] Existing polymer luminescent materials are generally prepared by physical blending, in which rare earth luminescent powders are directly dispersed in an engineering plastic matrix such as polyethersulfone. This method lacks chemical interaction between the rare earth powders and the polymer chains, leading to uncontrollable agglomeration and phase separation of the luminescent components within the matrix. This microscopically uneven distribution not only reduces the material's light transmittance but also causes local concentration quenching at the luminescent center, resulting in a decrease in the film's optical properties. To address these issues, the following solutions are proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified polyethersulfone composite membrane material and a preparation method thereof. By in situ constructing a picolinic acid-europium ion coordination structure in the polyethersulfone molecular chain, chemical bonding fixation of the luminescent center can be achieved, thereby solving the problem of agglomeration and phase separation of rare earth luminescent components caused by the lack of chemical interaction in the existing physical blending method.

[0005] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention relates to a modified polyethersulfone composite membrane material and a preparation method thereof. The composite membrane material comprises the following components, calculated by mass: 100 parts of a modified polyethersulfone matrix, 12-18 parts of picolinic acid side groups bonded to the matrix, and 4.0-5.5 parts of europium ions bonded to the picolinic acid side groups through bidentate coordination; the molar ratio of the picolinic acid side groups to the europium ions is 3:1.

[0007] Furthermore, the modified polyethersulfone matrix is ​​prepared by bisphenol A type polyethersulfone through a bromination-nucleophilic substitution reaction, and the bromination site is located in the benzene ring structure.

[0008] A method for preparing a modified polyethersulfone composite membrane material, comprising the following steps:

[0009] Step S1, polyethersulfone bromination modification: dissolving polyethersulfone in a solvent, adding a bromination reagent in batches at a specific temperature to react, and introducing bromine atoms as reaction sites on the molecular chain;

[0010] Step S2, picolinic acid side group grafting: adding picolinic acid to the brominated polyethersulfone solution, heating and reacting under the protection of inert gas, so that the picolinic acid replaces the bromine atom and is connected to the polyethersulfone chain;

[0011] Step S3, europium ion coordination reaction: cooling the system, slowly adding the europium salt solution dropwise to the solution containing the picolinic acid-modified polyethersulfone, and reacting under mild conditions to allow the europium ions to chemically coordinate with the picolinic acid groups;

[0012] Step S4, film casting: the reaction solution is cooled and filtered, poured onto a clean glass plate and scraped into a uniform liquid film, which is then evaporated at room temperature for a long time and dried at a programmed temperature gradient to remove the solvent;

[0013] Step S5, film stripping and post-processing: the dried film is immersed in water and peeled off, the surface moisture is absorbed, and then placed in a desiccator for equilibrium, and finally a modified polyethersulfone composite membrane material with chemically bonded europium ion luminescent centers is obtained.

[0014] Furthermore, the step S1, bromination modification of polyethersulfone specifically comprises the following steps:

[0015] Step S11: adding bisphenol A polyethersulfone particles into a three-necked flask filled with N,N-dimethylformamide, placing the flask in an oil bath and installing a mechanical stirrer, a condenser and a thermometer;

[0016] Step S12: turning on the stirrer and stirring at a speed of 300 rpm-500 rpm, raising the temperature to 70° C. to completely dissolve the polyethersulfone to form a transparent solution;

[0017] Step S13: maintaining the reaction temperature at 75±2° C., adding N-bromosuccinimide to the solution in batches, with each batch adding 5 g to 7 g and the interval between each batch addition being 10 minutes;

[0018] Step S14: After all the bromination reagents are added, the reaction is continued at a constant temperature for 4 hours to obtain a light yellow viscous brominated polyethersulfone solution;

[0019] This step introduces a bromine atom active site on the benzene ring of the polyethersulfone molecular chain. Through an electrophilic substitution reaction with N-bromosuccinimide at 75°C, the bromine atom is bonded to the PES backbone, forming a brominated polyethersulfone intermediate, which provides a chemical anchor point for subsequent grafting reactions.

[0020] Furthermore, the step S2, picolinic acid side group grafting specifically comprises the following steps:

[0021] Step S21: Add 15 g of 4-pyridinecarboxylic acid solid to the pale yellow viscous solution after bromination modification;

[0022] Step S22: The reaction system was heated to 110±5°C, and nitrogen was continuously introduced at a flow rate of 50 mL / min to provide atmosphere protection;

[0023] Step S23: Maintaining constant temperature for 8 hours, during which the color of the solution gradually changes from light yellow to brownish red;

[0024] This step utilizes the bromination site to achieve chemical bonding of the luminescent ligand; 4-pyridinecarboxylic acid undergoes a nucleophilic substitution reaction with brominated PES under nitrogen protection at 110°C, and its carboxyl end is covalently linked to the PES chain. The pyridine ring is exposed to the outside of the molecule as a coordinating group, constructing a polymer skeleton with coordination ability.

[0025] Furthermore, the europium ion coordination reaction in step S3 specifically includes the following steps:

[0026] Step S31: Cool the system to 60°C and maintain a nitrogen atmosphere;

[0027] Step S32: dissolving 6.58 g of europium nitrate trihydrate in 50 mL of anhydrous ethanol to form a europium salt solution, and slowly adding the solution dropwise to the reaction solution containing picolinic acid-modified polyethersulfone through a constant pressure dropping funnel at a rate of 2 mL / min;

[0028] Step S33: After the dropwise addition is completed, the reaction is maintained at a constant temperature of 60° C. with stirring for 3 hours, so that the pyridine nitrogen atom of the picolinic acid side group and the carboxyl oxygen atom cooperate to capture the europium ion to form a bidentate coordination bond, ultimately obtaining an orange-red transparent homogeneous solution;

[0029] This step realizes the in-situ bonding and dispersion of the luminescent center; under mild conditions of 60°C, the Eu in the europium nitrate ethanol solution 3+ It undergoes bidentate coordination with the nitrogen atom and carboxyl oxygen atom of picolinic acid to form a stable six-membered ring chelate structure, allowing the europium ion to be chemically bonded to the polymer network in a molecularly dispersed state.

[0030] Furthermore, the step S4, the film casting specifically includes the following steps:

[0031] Step S41: stopping heating, cooling the reaction solution to room temperature, and filtering the solution through a 400-mesh stainless steel filter to remove trace gel particles;

[0032] Step S42: Pour the filtered clarified solution onto a horizontally placed clean glass plate, and use a scraper to carefully spread the solution into a liquid film with a uniform thickness of 1.0±0.1 mm;

[0033] Step S43: The glass plate carrying the liquid film is transferred to a fume hood and allowed to stand at room temperature for 12 hours to allow the solvent to evaporate naturally;

[0034] Step S44: moving the glass plate into a blast drying oven and drying it according to a set gradient temperature program: first baking at 60°C for 2 hours, then heating to 80°C for 2 hours, and then heating to 100°C for 1 hour;

[0035] Step S45: placing the glass plate in a vacuum drying oven at 120° C. and maintaining a vacuum degree of -0.1 MPa, and continuing the drying process for 4 hours to remove all residual solvent and form a bubble-free, densely structured solid film;

[0036] This step converts the polymer solution into a solid functional film; after purification by filtration, the coating thickness is controlled to 1.0 mm, and a step-by-step drying procedure (60°C → 120°C) is used to allow the solvent to evaporate and eliminate internal stress, ultimately forming a defect-free, dense preformed film.

[0037] Furthermore, the step S5, demolding and post-processing specifically includes the following steps:

[0038] Step S51: immersing the dried glass plate in deionized water to allow the film to peel off naturally by the penetration of water;

[0039] Step S52: Use tweezers to pick up the edge of the film and transfer it to the filter paper, gently press to absorb the residual moisture on the surface;

[0040] Step S53: The film is then spread flat in a clean desiccator and allowed to stand at room temperature for 24 hours to obtain a light red transparent modified polyethersulfone composite membrane material with a thickness of 0.12±0.02 mm;

[0041] This step obtains a finished luminescent material that can be used independently; the film is gently peeled off from the glass substrate using the water immersion method. After water absorption, drying and balanced storage, an independent composite film with a thickness of 0.12 mm and uniform chemically bonded luminescent centers is obtained, which can be directly used as a solid-state luminescent material.

[0042] The present invention has the following beneficial effects:

[0043] The present invention realizes chemical bonding fixation of the luminescence center by in-situ constructing a picolinic acid-europium ion coordination structure in the polyethersulfone molecular chain; this design avoids the phase separation and luminescence component agglomeration problems inherent in the physical blending method, and improves the optical uniformity and long-term stability of the material; the luminescence center is dispersed at the molecular level in the polymer matrix, ensuring the simultaneous optimization of the film's light transmittance and luminescence efficiency, while effectively suppressing the fluorescence quenching phenomenon during use; the chemical bonding mechanism enhances the interaction force between the europium ions and the polymer chain, so that the material can still maintain structural integrity under thermal and mechanical stress, overcoming the defect of easy detachment of the surface coating layer; in terms of process, precise grafting and coordination of functional groups are achieved through step-by-step controllable reactions, ensuring the repeatability of the distribution of the luminescence center, and the film formation process adopts a gradient drying procedure to avoid the formation of defects caused by internal stress.

[0044] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0046] Figure 1 The present invention is a schematic flow chart of a method for preparing a modified polyethersulfone composite membrane material. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0048] See also Figure 1 As shown, the present invention is a method for preparing a modified polyethersulfone composite membrane material, comprising the following steps:

[0049] Step S1, polyethersulfone bromination modification: polyethersulfone is dissolved in a solvent, and a bromination reagent is added in batches at a specific temperature to react, thereby introducing bromine atoms as reaction sites on the molecular chain, specifically:

[0050] Step S11: adding bisphenol A polyethersulfone particles into a three-necked flask filled with N,N-dimethylformamide, placing the flask in an oil bath and installing a mechanical stirrer, a condenser and a thermometer;

[0051] Step S12: turning on the stirrer and stirring at a speed of 300 rpm-500 rpm, raising the temperature to 70° C. to completely dissolve the polyethersulfone to form a transparent solution;

[0052] Step S13: maintaining the reaction temperature at 75±2° C., adding N-bromosuccinimide to the solution in batches, with each batch adding 5 g to 7 g and the interval between each batch addition being 10 minutes;

[0053] Step S14: After all the bromination reagents are added, the reaction is continued at a constant temperature for 4 hours to obtain a light yellow viscous brominated polyethersulfone solution.

[0054] Step S2, picolinic acid side group grafting: add picolinic acid to the brominated polyethersulfone solution, increase the temperature and react under the protection of inert gas, so that the picolinic acid replaces the bromine atom and is connected to the polyethersulfone chain, specifically:

[0055] Step S21: Add 15 g of 4-pyridinecarboxylic acid solid to the pale yellow viscous solution after bromination modification;

[0056] Step S22: The reaction system was heated to 110±5°C, and nitrogen was continuously introduced at a flow rate of 50 mL / min to provide atmosphere protection;

[0057] Step S23: Maintaining constant temperature for 8 hours, during which the color of the solution gradually changes from light yellow to brownish red;

[0058] The in-situ coordination reaction achieves uniform molecular-scale dispersion of europium ions within the matrix, eliminating local concentration gradients caused by physical doping. The picolinic acid groups, acting as pre-designed coordination sites, control the uniform coordination environment of each europium ion, ensuring consistent energy levels across all luminescence centers. This molecular-level uniformity enhances the material's luminescence efficiency and minimizes excitation energy loss during transfer. Furthermore, the rigid structure of the coordination bonds effectively shields the europium ions from the quenching effect of water molecules, enabling the material to maintain high-color-purity luminescence even in complex environments, providing a foundation for reliable performance in optical devices.

[0059] Step S3, europium ion coordination reaction: the system is cooled, and the europium salt solution is slowly added dropwise to the solution containing picolinic acid-modified polyethersulfone, and the reaction is carried out under mild conditions to allow the europium ions to chemically coordinate with the picolinic acid groups, specifically:

[0060] Step S31: Cool the system to 60°C and maintain a nitrogen atmosphere;

[0061] Step S32: dissolving 6.58 g of europium nitrate trihydrate in 50 mL of anhydrous ethanol to form a europium salt solution, and slowly adding the solution dropwise to the reaction solution containing picolinic acid-modified polyethersulfone through a constant pressure dropping funnel at a rate of 2 mL / min;

[0062] Step S33: After the dropwise addition is completed, the reaction is maintained at a constant temperature of 60° C. with stirring for 3 hours, so that the pyridine nitrogen atom of the picolinic acid side group and the carboxyl oxygen atom cooperate to capture the europium ion to form a bidentate coordination bond, ultimately obtaining an orange-red transparent homogeneous solution;

[0063] A chemical bonding strategy is used to construct europium ion coordination centers in situ on the polyethersulfone molecular chain, resolving the component migration and phase separation issues encountered in physical blending methods. The bidentate coordination of the picolinic acid side groups forms a strong bonding network, firmly anchoring the luminescent center within the polymer matrix. This structure inhibits the dissociation and shedding of europium ions in humid and hot environments or under mechanical stress, slowing the luminescence decay of the material during use. Furthermore, chemical bonding blocks the tendency of luminescent components to aggregate due to molecular thermal motion, ensuring the stability of the material's optical properties over long-term service and overcoming the lifespan limitations of traditional blends due to poor interfacial compatibility.

[0064] Step S4, film casting: After the reaction liquid is cooled and filtered, it is poured onto a clean glass plate and scraped into a uniform liquid film, which is then evaporated at room temperature for a long time and dried at a programmed temperature gradient to remove the solvent, specifically:

[0065] Step S41: stopping heating, cooling the reaction solution to room temperature, and filtering the solution through a 400-mesh stainless steel filter to remove trace gel particles;

[0066] Step S42: Pour the filtered clarified solution onto a horizontally placed clean glass plate, and use a scraper to carefully spread the solution into a liquid film with a uniform thickness of 1.0±0.1 mm;

[0067] Step S43: The glass plate carrying the liquid film is transferred to a fume hood and allowed to stand at room temperature for 12 hours to allow the solvent to evaporate naturally;

[0068] Step S44: moving the glass plate into a blast drying oven and drying it according to a set gradient temperature program: first baking at 60°C for 2 hours, then heating to 80°C for 2 hours, and then heating to 100°C for 1 hour;

[0069] Step S45: placing the glass plate in a vacuum drying oven at 120° C. and maintaining a vacuum degree of -0.1 MPa, and continuing the drying process for 4 hours to remove all residual solvent and form a bubble-free, densely structured solid film;

[0070] The chemical bonding process enables the simultaneous formation of the luminescent function and the matrix material, avoiding secondary processing damage to the finished film caused by traditional post-modification methods; during the film formation process, the polymer chains and the luminescent centers synergistically self-assemble to form a homogeneous system without a phase interface, giving the material excellent optical transparency and mechanical continuity; this integrated preparation method eliminates additional steps such as pre-dispersion of luminescent powders and surface coating, simplifying the production process while reducing the generation of interface defects; the resulting composite film has high toughness, low internal stress and good surface flatness, and its comprehensive mechanical properties are comparable to those of the unmodified substrate, overcoming the embrittlement or delamination problems often associated with physical composite methods.

[0071] Step S5, film stripping and post-processing: the dried film is immersed in water and peeled off, the surface moisture is absorbed, and then the film is placed in a desiccator for equilibrium, and finally a modified polyethersulfone composite membrane material with a chemically bonded europium ion luminescent center is obtained, specifically:

[0072] Step S51: immersing the dried glass plate in deionized water to allow the film to peel off naturally by the penetration of water;

[0073] Step S52: Use tweezers to pick up the edge of the film and transfer it to the filter paper, gently press to absorb the residual moisture on the surface;

[0074] Step S53: The film is then spread flat in a clean desiccator and allowed to stand at room temperature for 24 hours to obtain a light red transparent modified polyethersulfone composite membrane material with a thickness of 0.12±0.02 mm.

[0075] A specific application of this embodiment is:

[0076] Example 1

[0077] Raw materials and equipment

[0078] Raw materials: Bisphenol A polyethersulfone (PES, Mn = 50,000): 100.0 g; Anhydrous N,N-dimethylformamide (DMF, water content ≤ 0.01%): 800 mL; N-bromosuccinimide (NBS, purity ≥ 98%): 25.0 g; 4-picolinic acid (purity ≥ 99%, TCI): 15.0 g; Europium nitrate trihydrate (Eu(NO3)3·3H2O, purity 99.99%): 6.58 g; Anhydrous ethanol (chromatographic grade): 50 mL;

[0079] Equipment: 2 L three-necked flask (jacketed); mechanical stirrer (I KARW20, equipped with polytetrafluoroethylene blades); constant temperature oil bath (temperature control accuracy ±0.5°C); constant pressure dropping funnel (100 mL); 400-mesh stainless steel filter (diameter 150 mm); glass plate (300 × 300 × 5 mm, surface roughness Ra ≤ 0.1 μm); stainless steel scraper (edge ​​clearance 1.0 mm);

[0080] Step S1, bromination modification of polyethersulfone: 800 mL of anhydrous N,N-dimethylformamide was injected into a 2L three-necked flask, and an agitator, condenser, and thermometer were installed; 100.0 g of bisphenol A type polyethersulfone particles were added, the oil bath was heated to 70°C, and stirred at 300 rpm until completely dissolved (about 40 minutes); N-bromosuccinimide was added in 5 batches (5.0 g per batch, with an interval of 10 minutes), and the temperature was maintained at 75±1°C; after the addition was completed, the reaction was kept at 75°C for 4 hours, and the solution became light yellow and viscous.

[0081] Step S2, picolinic acid side group grafting: add 15.0 g of 4-picolinic acid to the reaction solution; raise the temperature to 110±2° C., and introduce nitrogen (50 mL / min) to remove air; and stir the reaction at constant temperature for 8 hours until the solution turns into a uniform brown-red color.

[0082] Step S3, europium ion coordination: cool to 60±1°C and maintain a nitrogen atmosphere; dissolve 6.58g Eu(NO3)3·3H2O in 50mL anhydrous ethanol and add dropwise at a rate of 2mL / min through a dropping funnel; continue the reaction for 3 hours after the addition is complete, and the solution becomes transparent orange-red;

[0083] Step S4, film casting: stop heating and cool naturally to 25°C; filter the solution under pressure through a 400-mesh filter into a clean beaker; pour the filtrate onto a horizontally calibrated glass plate; apply the film with a scraper at a constant speed (10 cm / s) to control the wet film thickness to 1.0±0.05 mm; volatilize under ventilation at room temperature for 12 hours (humidity ≤ 40%); gradient drying: 60°C / 2h → 80°C / 2h → 100°C / 1h in a forced air drying oven; vacuum drying oven (-0.098 MPa) 120°C / 4h.

[0084] Step S5, film removal and post-processing: immerse the glass plate in 30° C. deionized water and let it stand for 5 minutes to allow the film to peel off naturally; use dust-free filter paper to absorb the moisture on the film surface; and store it in a desiccator (silica gel desiccant) for 24 hours.

[0085] Example 2

[0086] Raw materials and equipment adjustments are shown in the following table:

[0087]

[0088] Step S1, Bromination Modification of Polyethersulfone: In a nitrogen glove box, 100 g of PES pellets were added to a 2 L three-necked flask containing 700 mL of sulfolane; the oil bath was heated to 130° C. and stirred to dissolve (approximately 1 hour); NBS was added in 6 batches (4.17 g per batch, with 8-minute intervals), maintaining the temperature at 130±2° C.; and the mixture was reacted for 5 hours to obtain a brown solution (the bromination rate increased to 25%).

[0089] Step S2, grafting of thiophenecarboxylic acid side groups: adding 12.8 g of thiophene-2-carboxylic acid; raising the temperature to 150±2° C., passing argon gas (60 mL / min); reacting for 10 hours, and the solution turned into a dark green viscous liquid.

[0090] Step S3, terbium ion coordination: cool to 50°C, dissolve 7.23g of TbCl3·6H2O in 40mL of anhydrous methanol; inject into the reaction system at a rate of 1mL / min via a syringe pump; react at constant temperature for 4 hours, and the solution becomes transparent yellow-green;

[0091] Step S4, spin coating: The reaction solution was cooled to 80° C. (to maintain fluidity), and pressure filtered through a 0.45 μm PTFE filter membrane; 10 mL of the filtrate was dropped onto the center of a vacuum-adsorbed silicon wafer;

[0092] Spin coating procedure:

[0093] Stage 1: 500 rpm / 10 s (spreading);

[0094] Second stage: 2000rpm / 30s (thickness control);

[0095] The third stage: 5000rpm / 60s (leveling);

[0096] Immediately move the mixture into a vacuum desiccator (-0.1 MPa) and keep it away from light for 2 hours.

[0097] Step S5: thermal curing treatment:

[0098] Programmed temperature curing (nitrogen atmosphere), as shown in the following table:

[0099]

[0100] After the temperature naturally dropped to 60°C, the silicon wafer was taken out.

[0101] Step S6, water-assisted demolding: Tilt the silicon wafer into ultrapure water (25°C), clamp the edge of the membrane with tweezers and slowly peel it off; transfer the film floating on the water surface to a porous PTFE plate; and equilibrate in a drying chamber (RH≤10%) for 48 hours.

[0102] The comparison between Example 1 and Example 2 is shown in the following table:

[0103]

[0104] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0105] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A modified polyethersulfone composite membrane material, characterized in that: The composite membrane material includes the following components in parts by mass: 100 parts of a modified polyethersulfone matrix, 12-18 parts of picolinic acid side groups bonded to the matrix, and 4.0-5.5 parts of europium ions bonded to the picolinic acid side groups through bidentate coordination; the molar ratio of the picolinic acid side groups to the europium ions is 3:

1.

2. A modified polyethersulfone composite membrane material according to claim 1, characterized in that: The modified polyethersulfone matrix is ​​prepared from bisphenol A type polyethersulfone through a bromination-nucleophilic substitution reaction, and the bromination site is located at the benzene ring structure.

3. A method for preparing a modified polyethersulfone composite membrane material, characterized in that: The preparation method comprises the following steps: Step S1, polyethersulfone bromination modification: dissolving polyethersulfone in a solvent, adding a bromination reagent in batches at a specific temperature to react, and introducing bromine atoms as reaction sites on the molecular chain; Step S2, picolinic acid side group grafting: adding picolinic acid to the brominated polyethersulfone solution, heating and reacting under the protection of inert gas, so that the picolinic acid replaces the bromine atom and is connected to the polyethersulfone chain; Step S3, europium ion coordination reaction: cooling the system, slowly adding the europium salt solution dropwise to the solution containing the picolinic acid-modified polyethersulfone, and reacting under mild conditions to allow the europium ions to chemically coordinate with the picolinic acid groups; Step S4, film casting: the reaction solution is cooled and filtered, poured onto a clean glass plate and scraped into a uniform liquid film, which is then evaporated at room temperature for a long time and dried at a programmed temperature gradient to remove the solvent; Step S5, film stripping and post-processing: the dried film is immersed in water and peeled off, the surface moisture is absorbed, and then placed in a desiccator for equilibrium, and finally a modified polyethersulfone composite membrane material with chemically bonded europium ion luminescent centers is obtained.

4. The method for preparing a modified polyethersulfone composite membrane material according to claim 3, characterized in that: The step S1, bromination modification of polyethersulfone specifically comprises the following steps: Step S11: adding bisphenol A polyethersulfone particles into a three-necked flask filled with N,N-dimethylformamide, placing the flask in an oil bath and installing a mechanical stirrer, a condenser and a thermometer; Step S12: turning on the stirrer and stirring at a speed of 300 rpm-500 rpm, raising the temperature to 70° C. to completely dissolve the polyethersulfone to form a transparent solution; Step S13: maintaining the reaction temperature at 75±2° C., adding N-bromosuccinimide to the solution in batches, with each batch adding 5 g to 7 g and the interval between each batch addition being 10 minutes; Step S14: After all the bromination reagents are added, the reaction is continued at a constant temperature for 4 hours to obtain a light yellow viscous brominated polyethersulfone solution.

5. The method for preparing a modified polyethersulfone composite membrane material according to claim 3, characterized in that: The step S2, picolinic acid side group grafting specifically comprises the following steps: Step S21: Add 15 g of 4-pyridinecarboxylic acid solid to the pale yellow viscous solution after bromination modification; Step S22: The reaction system was heated to 110±5°C, and nitrogen was continuously introduced at a flow rate of 50 mL / min to provide an atmosphere protection; Step S23: Maintaining constant temperature for 8 hours, during which the color of the solution gradually changes from light yellow to brownish red.

6. The method for preparing a modified polyethersulfone composite membrane material according to claim 3, characterized in that: The europium ion coordination reaction in step S3 specifically comprises the following steps: Step S31: Cool the system to 60°C and maintain a nitrogen atmosphere; Step S32: dissolving 6.58 g of europium nitrate trihydrate in 50 mL of anhydrous ethanol to form a europium salt solution, and slowly adding the solution dropwise to the reaction solution containing picolinic acid-modified polyethersulfone through a constant pressure dropping funnel at a rate of 2 mL / min; Step S33: After the dropwise addition is completed, the mixture is stirred at 60° C. for 3 hours to allow the pyridine nitrogen atom of the picolinic acid side group and the carboxyl oxygen atom to cooperatively capture the europium ion to form a bidentate coordination bond, ultimately obtaining an orange-red transparent homogeneous solution.

7. The method for preparing a modified polyethersulfone composite membrane material according to claim 3, characterized in that: The step S4, the film casting, specifically comprises the following steps: Step S41: stopping heating, cooling the reaction solution to room temperature, and filtering the solution through a 400-mesh stainless steel filter to remove trace gel particles; Step S42: Pour the filtered clarified solution onto a horizontally placed clean glass plate, and use a scraper to carefully spread the solution into a liquid film with a uniform thickness of 1.0±0.1 mm; Step S43: The glass plate carrying the liquid film is transferred to a fume hood and allowed to stand at room temperature for 12 hours to allow the solvent to evaporate naturally; Step S44: moving the glass plate into a blast drying oven and drying it according to a set gradient temperature program: first baking at 60°C for 2 hours, then heating to 80°C for 2 hours, and then heating to 100°C for 1 hour; Step S45: The glass plate is placed in a vacuum drying oven at a temperature of 120° C. and a vacuum degree of −0.1 MPa, and the drying process is continued for 4 hours to remove all residual solvents and form a solid film with no bubbles and a dense structure.

8. A modified polyethersulfone composite membrane material and a preparation method thereof according to claim 3, characterized in that: The step S5, demolding and post-processing specifically includes the following steps: Step S51: immersing the dried glass plate in deionized water to allow the film to peel off naturally by the penetration of water; Step S52: Use tweezers to pick up the edge of the film and transfer it to filter paper, gently press to absorb any remaining moisture on the surface; Step S53: The film is then spread flat in a clean desiccator and allowed to stand at room temperature for 24 hours to obtain a light red transparent modified polyethersulfone composite membrane material with a thickness of 0.12±0.02 mm.

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